Set the script of the field to the following RevTalk code. Read the comments for an explanation of what is going on.

local sMementoA

-- message sent by the Revolution engine when

-- focus enters the field

on openField

## Store content of field so we can undo changes the

## user makes. No undo entry is made here however

## as the user hasn't made any changes yet.

put the long id of the target into sMementoA["field"]

put the htmltext of the target into sMementoA["htmltext"]

pass openField

end openField

-- message sent by the Revolution engine when focus

-- leaves the field and the user has changed the field

-- contents by typing

on closefield

LogUndoIfNecessary

pass closefield

end closefield

-- message sent by the Revolution engine when focus

-- leaves the field and the user has NOT changed the field

-- contents by typing. Content could have been changed

-- by RevTalk code though so we need to check whether

-- or not an undo should be logged.

on exitField

LogUndoIfNecessary

pass exitField

end exitField

command LogUndoIfNecessary

## If the content of the field has changed since the openField

## message was received then add an undo action to the queue

## 'the target' will always be the field as this command is

## called from closeField and exitField.

if the htmltext of the target is not sMementoA["htmltext"] then

undoStoreUndo "edit field content", "Edit Text", sMementoA

end if

## Clear memory

put empty into sMementoA

end LogUndoIfNecessary

Click inside the field. This triggers the openField message. Edit the text. Even though a change has been made the undo manager doesn't know about it yet and doesn't post an undo action to the queue. An undo action will be posted to the queue when the closeField or exitField message is received.

Clicking outside the field triggers the closeField message which in turn posts an Undo Action to the Undo Queue.

The text will change to the original value and a dialog will appear showing you what happened.